1. Field of the Invention
The present invention relates to a connecting structure for connecting a vacuum pump. In particular, it relates to a connecting structure for a vacuum pump, which is capable of blocking propagation of electrical noise generated by a main body of the vacuum pump.
2. Description of the Related Art
A conventional connecting structure used for connecting a vacuum pump (hereinafter referred to as the “connecting structure for a vacuum pump) is shown in FIG. 6.
Referring to FIG. 6, when a vacuum pump 101 is connected through connection piping to a measuring apparatus such as an electron microscope which requires a vibration-free environment to operate, a damper 105 as a vibration absorbing member is interposedly disposed within the connection piping. Electron microscope etc. are provided in a vacuum chamber 103 being a measurement chamber. The vacuum pump 101 is suspended from the vacuum chamber 103 with the damper 105 so as to be connected thereto.
The damper 105 is constructed so that a bellows 105a is sandwiched between flanges 107 and 109 arranged on its both ends. The bellows 105a absorbs vibrations between a suction port of the vacuum pump 101 and the vacuum chamber 103.
The bellows 105a is formed of a stainless material in order to have a mechanical strength sufficient to protect itself in an event of the vacuum pump 101 being broken due to centrifugal force.
Connection between the damper 105 and the vacuum chamber 103 is provided by means of the flange 109 formed at the upper end of the damper 105 and a flange 113 of the vacuum chamber 103. Connection between the damper 105 and the vacuum pump 101 is provided by means of the flange 107 formed at the lower end of the damper 105 and a suction flange 111 of the vacuum pump 101.
In the thus constructed connecting structure for the vacuum pump 101, operating the vacuum pump 101 for suction and decompression purposes allows decompression of the vacuum chamber 103 to be effected from the suction port of the vacuum pump 101 through the connection piping. At this time, vibrations are generated by a main body of the vacuum pump 101 due to such factors as an unbalanced state of a rotor and cogging torque acting during a rotational drive. Such mechanical vibrations of the vacuum pump 101 are blocked out by the damper 105, whereby the vibrations do not reach the vacuum chamber 103 so that a vibration-free environment can be maintained.
However, in the above construction, the damper 105 which constitutes the above-described connection piping is formed of a material with high electrical conductivity such as a stainless material, including its portions of the both flanges 107 and 109. This may lead to a troublesome situation where electrical noise generated by electric equipment such as a motor disposed within the vacuum pump 101 propagates into an apparatus to be connected with the vacuum pump 101. In particular, in a case of a measuring apparatus, which requires for its operation an environment isolated of disturbances such as mechanical vibrations and electrical noise, even if it is effectively guarded against intrusion of disturbances from the outside, disturbances generated by an associated apparatus such as the vacuum pump 101 connected to the measuring apparatus may induce reduction in the measurement accuracy thereof.